Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$97.61	8.859%	$106.2573	$106.26	$106.25	$106.30
Purchase #2	$72.81	13.307%	$82.4988	$82.50	$82.50	$82.50
Purchase #3	$152.68	8.468%	$165.6089	$165.61	$165.60	$165.60
Purchase #4	$185.65	7.630%	$199.8151	$199.82	$199.80	$199.80
Purchase #5	$104.80	6.322%	$111.4255	$111.43	$111.45	$111.40
Purchase #6	$17.42	3.818%	$18.0851	$18.09	$18.10	$18.10
Purchase #7	$238.84	11.445%	$266.1752	$266.18	$266.20	$266.20
7 purchase totals =	$869.81		$949.8659	$949.89	$949.90	$949.90